The Liquid Crystal Display (LCD) possesses advantages of thin body, power saving and no radiation to be widely used in many application scope, such as LCD TV, mobile phone, personal digital assistant (PDA), digital camera, notebook, laptop, and dominates the flat panel display field.
Most of the liquid crystal displays on the present market are backlight type liquid crystal displays, which comprise a liquid crystal display panel and a backlight module. The working principle of the liquid crystal display panel is that the Liquid Crystal is injected between the Thin Film Transistor Array Substrate (TFT array substrate) and the Color Filter (CF). The light of backlight module is refracted to generate images by applying driving voltages to the two substrates for controlling the rotations of the liquid crystal molecules.
The Active Matrix Liquid Crystal Display (AMLCD) is the most common liquid crystal display device at present. The Active Matrix Liquid Crystal Display comprises a plurality of pixels, and each pixel comprises a Thin Film Transistor (TFT). The gate of the TFT is coupled to the scan line extending along the horizontal direction. The drain of the TFT is coupled to the data line extending along the vertical direction. The source of the TFT is coupled to the corresponding pixel electrode. When a sufficient positive voltage is applied to some scan line in the horizontal direction, all the TFT coupled to the scan line will be activated to write the data signal loaded in the data line into the pixel electrodes and thus to show images to control the transmittances of different liquid crystals to achieve the effect of controlling colors.
The driving of the level scan line (i.e. the gate driving) in the present active liquid crystal display is initially accomplished by the external Integrated Circuit (IC). The external IC can control the charge and discharge stage by stage of the level scan lines of respective stages. The GOA technology, i.e. the Gate Driver on Array technology can utilize the array manufacture processes of the liquid crystal display panel to manufacture the driving circuit of the level scan lines on the substrate around the active area, to replace the external IC for accomplishing the driving of the level scan lines. The GOA technology can reduce the bonding procedure of the external IC and has potential to raise the productivity and lower the production cost. Meanwhile, it can make the liquid crystal display panel more suitable to the narrow frame design of display products.
At present, the GOA technology has been widely applied in the liquid crystal display panel. However, the GOA circuit according to prior art has drawbacks of increasing power consumption in comparison with the externally connected IC. AS shown in FIG. 1, a GOA circuit according to prior art comprises a plurality of GOA unit circuits which are cascade connected, and in the GOA unit circuit of the Nth stage, both the gate and the source of the eleventh thin film transistor T11 receives the stage transfer signal ST(N−1) of the GOA unit circuit of the former N−1th stage to be in charge of pull-up control; the source of the twenty-first thin film transistor T21 receives a clock signal CK(m), and as the gate is at high voltage level, the twenty-first thin film transistor T21 is activated, and the drain outputs the clock signal CK(m) to be the scan driving signal G(N) to pull up the scan driving signal G(N).
The calculation formula of power consumption is:P=½CfV2 
wherein P represents the power consumption, and f represents the frequency of the signal, and C represents the capacitance of the signal line, and V represents the high-low voltage level difference of the signal line. In the GOA circuit shown in FIG. 1, the frequency of the clock signal CK(m) is the highest, which is equal thousands times of other signal frequencies. This is the reason why the power consumption of the GOA circuit is larger, which mainly is generated by the clock signal CK(m). The power consumption, frequency of the signal, the capacitance of the signal line, the high-low voltage level difference of the signal line are in direct proportion, wherein the frequency is related to the resolution of the liquid crystal display panel and cannot be changed. Therefore, only the capacitance or the voltage difference can be decreased for reducing the power consumption.
Besides, the scan driving signal also needs to receive signals from the gate and the source of the eleventh thin film transistor T11 of the GOA unit circuit of the latter stage, and the loading of the scan driving signal G(N) is larger. Once the GOA circuit shown in FIG. 1 requires adjusting the high voltage level of the scan driving signal G(N) to enhance the propulsive force and the charge ability to the TFTs in the active area, it has to be achieved by raising the high voltage of the clock signal CK(m). Under such circumstance, it results in larger high-low voltage difference of the clock signal CK(m), and the power consumption of the GOA circuit is higher. However, if the high voltage of the clock signal CK(m) is not raised, then the propulsive force of the scan driving signal G(N) will be insufficient, which can easily cause the abnormal sequence of the scan driving signal G(N).